Coloring metals.



UNITE STATES SALOMON AXELROD, OF OBERSCI'IONEWEIDE, GERMANY, ASSIGNOR TOGENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

QOLORING- METALS. I

No Drawing.

Specification of Letters latent.

Patented Apr. 16, mic.

Application filed December 16, 1908. Serial No. 467,802.

. When aluminium oxid is heated with oobalt salts, there is obtained adark blue mass of cobalt ultra-marine or Thenards blue. Zinc. oxid, inthe same manner, results in the so-called Rinmans green. Tin oxid iscolored blue-green and magnesium oxid flesh-color. I find that if thisreaction is carried out on a clean metallic surface of .the abovemetals, the same colors are. ob-

assumes a black color. The black coating thus produced adheres firmly tothe metal and protects it from corrosion.

According to my present knowledge, the reactions here taking place areas follows: The originally formed combination of the metallic oxid andthe cobalt salt, which, in all probability, consists of a double salt ofthe specific metal with the cobalt salt, unites with an excess of cobaltsalt, and using for example, cobaltous nitrate, the resulting compoundhas a steel gray color, often with a metallic luster, and it probablyhas been transformed into a se'squioxid .of cobalt. This in turn istransformed by a stronger heating to the cobaltous-cobalicaoxid. ,Inthis manner, it is possible to produce brown, steel-gray, and surfaceofthe specific metal by varying the heating temperature and; the excessof cobaltsalt. s

The manner of carrying out the foregoing procedure is as follows: Theobject to I be treated, either with previouswarming or while cold, isdipped into a neutral or alkaline solution of cobalt salt, such ascobaltous nitrate, and is subsequently gently, or more strongly heatedaccording to the shade deblack colorations upon the;

sired. If desired, the solution also may be painted on with a softbrush- The degree of temperature andthe number of immersions aredetermined entirely by the shade desired. I 2

It is true that processes are known for producing a brown color uponaluminium, as byv heating the metal after it has been provided with acoating, of fresh white-ofegg', but the coating produced in this mannercan be removed by energetic rubbing. According to the differentprocedure described by Dr. Getting, a brown color is produced uponaluminium by etching the metal, whereby the silicon and iron inthe-commercial aluminium are brought out and pro-'- duce a surfacecoloration. This ives the aluminium not a black, but a brownlsh color.

The progress caused by the present invention lies chiefly in the factthat the metal is given a surface, not consist-ing of some superficialcarbonaceous material, but a permaneiit dead-black metallic coatingfirmly adherent to the surface.

The present process also can be carried out relatively more cheaply andrapidly than processes used heretofore.

Although I have, described my invention with reference more particularlyto aluminium, I desire it to be understood that other metals such aszinc, tin, magnesium, and their alloys, and in fact any metals formingcolored compounds with cobalt salts may be treated in a similar manner,in order toproduce the above-described surface colorations.

I also mean by the appended claims to include the treatment of aluminiumor other metal surfaces which have a surface film of oxid.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. The process of producing a coating upon metals which consistsi'nproviding the metals with a surface coating of cobalt salt andsubsequently heating the metals moreor less strongly according to theshade de- 3. The process of surface-coloring metals P which consists inapplying upon the metals a neutral solution of cobalt salts and heatingthe same more or less strongly acc0rding. to the shade desired.

4. The process-0f surface-coloring metal which consists in applying uponthe surface of a metal, a coating of a cobalt compound and then heatingthe metal more or less strongly according to the shade of color desired.4

5. An aluminium article having a surface coating, chemically combinedtherewith, of an adherent cobalt compound.

6. A metallic article having a cobalt compound chemically combined withits surface.

7. A metallic article having a black 00- 15 I balt compound chemicallycombined with its surface.

8. An aluminium article having on its surface, chemically combinedtherewith, a black adherent compound of aluminium and 20 cobalt.

In witness whereof, I have hereunto set my hand this 24th day ofNovember, 1908.

SALOMON AXELROD.

WVitnesses: HARL BREKELEEN, ALFRED WOLF.

